How do index fossils scientists?
they aid in the study of ranges of different organisms.
they advance understanding of the origin of life on earth.
they aid in comparison of rock layers at distant locations.
they advance understanding of rock type at the time the organism lived.

They aid in comparison of rock layers at distant locations

Explanation:

Index fossils refers to fossils that originate from organisms that were distinct, abundant, located in distant geographical locations and only lived for a short period of time.

They help scientists to compare rock layers at distant locations.

They aid in comparison of rock layers at distant locations

Explanation:

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the more fit you are, the faster the recovery. your heart rate drops most sharply in the first minute after you stop exercising; it should then fall about 20 beats a minute—a drop of less than 12 beats a minute is considered abnormal. this “recovery heart rate” is measured as part of an exercise stress test.